1. Field of the Invention
The present invention relates to a method of and an apparatus for controlling a disk drive, which are contrived to reduce consumed electric power of the disk drive, and more particularly to a disk drive control method and apparatus suitable for a disk drive driven by a battery.
2. Related Background Art
A disk drive such as a magnetic disk drive, e.g., has widely been utilized as a storage device for a computer. The disk drive is, with its downsizing attained in recent years, mounted in a computer driven by a battery such as a note-type personal computer, e.g. A reduction in consumed electric power of the disk drive is required for this type of battery-driven apparatus.
The magnetic disk device, when performing a recording/reproducing operation, operates at a single spindle revolving speed. Then, a motor constant of the spindle motor is determined so that the spindle motor operates with a stability under all sorts of operating environments assured by the magnetic disk device.
This type of magnetic disk device has increasingly been mounted in the battery-driven apparatus such as the note-type personal computer, e.g. A power source capacity of the battery is limited, and hence a decrease in consumed electric power is requested of the magnetic disk device.
Such being the case, there is proposed a method of stopping the spindle motor if there is no access to the magnetic disk device for a fixed period of time from the host computer (Japanese Patent Application Laid-Open Publication No. 4-143961).
There arise the following problems inherent in the prior art.
(1) As the operation system for the personal computer in recent years frequently accesses the magnetic disk device in a normal using state, it is difficult to attain a state where the spindle motor stops. Therefore, a battery drive time is substantially hard to extend.
(2) Further, when accessing the magnetic disk device in the state where the spindle motor halts, the user must wait several seconds for performing the recording and reproducing until the revolutions of the spindle motor are stabilized. Therefore, smoothness of the operation is lost.
(3) Some of the magnetic disk devices have been developed in recent years in a way that a fluid dynamic pressure bearing is used as a bearing of the spindle motor. It is characteristic of the fluid dynamic pressure bearing that an accuracy of revolutions is enhanced and that noises are small. The fluid bearing has, however, such a tendency that as a temperature decreases, a fluid viscosity of the bearing rises, and a torque loss of the bearing unit increases. This torque loss leads directly to an increase in the consumed electric power of the magnetic disk device. Therefore, the consumed electric power largely increases at a low temperature as compared with a case at a normal temperature. Especially the note-type personal computer might be used under an environment where the temperature is as low as 5xc2x0 C. or under, which conduces to the problem that the consumed electric power rises.
(4) Moreover, in the case of executing the recording/reproducing operation only when the spindle motor operates at the single revolving speed, the spindle motor is so designed as to keep the revolving speed with a stability under a high-load condition. It is therefore required that a limit number of revolutions of the spindle motor, which is a maximum revolving speed when the spindle motor is revolved under a predetermined load and a predetermined drive voltage without controlling the speed, is high. Therefore, the spindle motor having a large quantity of consumed electric power is needed.
It is a primary object of the present invention, which was devised to obviate the above problems inherent in the prior art, to provide a method of and an apparatus for controlling a disk drive, which are contrived to reduce consumed electric power of a spindle motor of the disk drive.
It is another object of the present invention to provide a method of and an apparatus for controlling a disk drive, which are contrived to reduce consumed electric power while the operation continues.
It is a further object of the present invention to provide a method of and an apparatus for controlling a disk drive, which are contrived to prevent the consumed electric power from rising even when a load of the spindle motor increases.
It is a still further object of the present invention to provide a method of and an apparatus for controlling a disk drive, which are contrived to reduce the consumed electric power in accordance with a capacity of a power source such as a battery, e.g.
To accomplish the above objects, according to a first aspect of the present invention, there is provided a method of controlling a disk drive having a disk storage medium, a spindle motor for rotating the disk storage medium, and a head for reading data on the disk storage medium. The control method comprises a first step for detecting a load of the spindle motor or a load capacity of a power source of the disk drive, and a second step for selecting any one of a first mode of revolving the spindle motor at a comparatively high speed in accordance with a detected result and reading the data on the disk storage medium by the head, and a second mode of revolving the spindle motor at a comparatively low speed in accordance with a detected result and reading the data on the disk storage medium by the head.
Therefore, if a load of the spindle motor is high, the recording/reproducing process is executed with the low-speed revolutions, and hence the consumed electric power can be restrained from rising. Further, if the power source has a small capacity, the recording/reproducing process can be implemented with the low-speed revolutions, and the consumed electric power is decreased. Consequently, especially a battery drive time of a battery-driven apparatus can be extended.
Moreover, it is feasible to use a spindle motor exhibiting a high torque constant and a small limit number of revolutions, so that consumed electric power can be further reduced.
In the control method according to the second aspect of the invention, the second step comprises a step for selecting the second mode if the load is higher than a predetermined value or if the load capacity is smaller than a predetermined value.
In the control method according to the third aspect of the invention, the second step further comprises a step for retaining the second mode for a predetermined time after selecting the second mode. It is possible to prevent the first and second modes from being frequently switched over with a change in the load or the load capacity.
In the control method according to the fourth aspect of the invention, the second step comprises a step for, after selecting the second mode, returning to the first mode corresponding to the fact that the load of the spindle motor is lower than a second predetermined value, or that the load capacity is larger than a third predetermined value.
It is therefore feasible to prevent the first and second modes from being frequently switched over with the change in the load or the load capacity.
In the control method according to the fifth aspect of the invention, the first step comprises a step for detecting a temperature of the spindle motor. The operation can be switched over to a mode in which the consumed electric power is decreased by detecting a change in the load due to a variation in viscosity of a fluid dynamic pressure bearing of the spindle motor based on the temperature of the spindle motor.
In the control method according to the sixth aspect of the invention, the first step comprises a step for detecting a change in the number of revolutions of the spindle motor. The operation can be switched over to a mode in which the consumed electric power is decreased by detecting the change in the load due to the variation in viscosity of the fluid dynamic pressure bearing of the spindle motor based on the change in the number of revolutions of the spindle motor.
In the control method according to the seventh aspect of the invention, the first step comprises a step for detecting a voltage of the power source. The operation can be switched over to a low consumed power mode by detecting a residual capacity of the power source based on the voltage of the power source. Therefore the battery drive time can be extended.